Abstract
Physiological responses of 1-year-old Pinus densiflora and Larix kaempferi seedlings were measured under open-field warming and precipitation manipulation. Air temperature of warming plots was 3 °C higher, while precipitation manipulation plots received ±40% of the precipitation than control plots. Seedlings were planted in May, and temperature and precipitation were manipulated from June 2017. Total chlorophyll content (Chlt), net photosynthetic rate (Pn), transpiration rate (E), and stomatal conductance (gs) were measured between July and September 2017. For P. densiflora and L. kaempferi, Chlt increased by 11.75% and 11.64%, and Pn decreased by 9.14% and 2.17% under warming, respectively. E and gs were lower under warming in P. densiflora, but higher in L. kaempferi. The lower Pn in P. densiflora resulted from stomatal closure, while that of L. kaempferi resulted from reduced vitality. Lower precipitation increased Chlt and Pn by 11.64% and 2.66% for P. densiflora, and by 6.40% and 4.32% for L. kaempferi, respectively. Conversely, higher precipitation decreased Pn of P. densiflora by 5.72%, and decreased Chlt and Pn of L. kaempferi by 8.24% and 4.55%, respectively. These results can be attributed to concentrated precipitation. In this study, two species responded differently even when they were exposed to the same environmental conditions, and this was due to the species-specific mechanisms to water stress derived from the high temperature.
Highlights
According to the Intergovernmental Panel on Climate Change (IPCC), the climate is clearly changing, and the change is being observed across the world (IPCC 2014)
Net photosynthetic rate, transpiration rate, and stomatal conductance of P. densiflora and L. kaempferi were significantly affected by the warming treatment, and total chlorophyll content and net photosynthetic rate were significantly affected by the precipitation treatments
In TW plots, the net photosynthetic rate, transpiration rate, and stomatal conductance of P. densiflora were significantly higher by 9.14%, 30.33%, and 39.11%, respectively, than in temperature levels [control (TC) plots (Figure 2b–d)
Summary
According to the Intergovernmental Panel on Climate Change (IPCC), the climate is clearly changing, and the change is being observed across the world (IPCC 2014). The IPCC predicts a global increase in temperature, and either an increase or decrease in precipitation, depending on the region (IPCC 2014). These changes are expected to modify terrestrial ecosystems (Solomon et al 2007). It is predicted that climate change will affect forest ecosystems, including the energy flow, carbon and water circulation, and vegetation dynamics of forest ecosystems (Dale et al 2001; Bonan 2008; Lindner et al 2010). Climate change affects the physiological characteristics of trees, as these respond noticeably to changes in temperature and precipitation (Hughes 2000). Physiological characteristics affect the competitiveness and growth of tree species (Xu et al 2012), which in turn may affect the dynamics of forest ecosystems. Studies on physiology can help identify and predict ecosystem changes due to climate change (Po€rtner and Farrell 2008; Somero 2010)
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